The present invention relates to a circuit arrangement including a load transistor and a measuring transistor. In such a circuit arrangement, the measuring transistor serves for measuring a load current flowing through the load transistor. In this case, the measuring transistor is operated at the same operating point as the load transistor; a measurement current flowing through the measuring transistor is then directly proportional to a load current flowing through the load transistor. In this case, a proportionality factor between the measurement current and the load current is determined by a ratio between the active transistor area of the measuring transistor and the active transistor area of the load transistor.
For setting the operating point of the measuring transistor, a circuit arrangement of this type contains a regulating circuit having a measuring amplifier and a variable resistor connected in series with the measuring transistor. The measuring amplifier serves to detect a difference between electrical potentials at load path connections of the load transistor and of the measuring transistor and to readjust the resistance value of the resistor ideally in such a way that this potential difference is zero. If the measuring amplifier has a voltage offset, then this offset can adversely influence the setting of the operating point of the measuring amplifier, and thus the current measurement. The offset can have an adverse effect particularly in the case of small load currents, and thus in the case of small measurement currents.
For these and other reasons there is a need for the present invention.